Switch.



No. 860,124. PATENTED JULY 16, 1907. D. M. BLISS SWITCH,

Arrmonzow FILED JULY14. 1905.

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STATES PATENT OFFICE,

DONALD ELECTRIC COMPANY, A CORPORATION or MASSACHUSETTS.

FLISS, :OF BROOKLINE, MASSACHUSETTS, ASSIGiNOR TO HOLTZER GABOT SWITCH.

No. 860,124. A

' Specification of Letters Patent.

. Patented July 16, 1907...

Application filed July 14, 1905. Serial F0; 269,649.

To all nihom it may concern:

Be known that I, DONALD M. Btrss, a subject of the King of GreatBritain, residing in Brookline, in the county of Norfolk, State ofMassachusetts, have inaddition to the working winding, with a startingwinding in 'multiple with the working winding, the said starting windinhowever, being open-circuited after the rotor has rea heda'predetermined speed.

The present invention is embodied in an automatic switch for opening thecircuit through the starting coils, the purpose of the invention beingto obtain a switch which will open automatically after a certain is suchas to vary the leverage through which the spring acts, so that moreforce is required to move the switch from its closed to itsopenposition, than-is required to restore the switch to its closed positionafter it has once been opened.

A further feature of the invention consists in an arrangement wherebythe contact member of the switch is acted upon by centrifugal force insuch a manner as to insure a firm sliding contact during the firstopening movement of the switch and the final closing movement thereof.

Figure l isan elevation of the rotor member of an induction motorftheswitch mechanism being shown in section, the section taken on ,a line 96of Fig. 2; Fig. 2 is a section on the line 00 of Fig. 1, looking in thedirection of the arrow, and showing, in full and dotted lines, theswitch mechanism in elevation; Fig. 3 isa diagram of the stator circuitsand a partial view of the switch to illustrate the operation.

Referring to Fig. 3, the current is supplied to the stator from the lineconductors 2 and 3, the working coils A being directly connected withthe line terminals at the points 20 and 30. One terminal of the startingwinding B is connected with the line 2 at 20, while the other terminalleads through a conductor 4 to a brush 5.which bears upon a collectorring a-, the circuit being completed through a brush 6 bearing upon acollector ring b and a conductor 7 which leads to the terminal 30. Solong, therefore, as the collector rings a and b are electricallyconnected, current will flow in multiple circuit through both thewindings A and B. It is desirable, however, to cutout the starting coilsB after the rotor has reached a predetermined speed,'and, for thispurpose, the connection between the collector rings a and b is arrangedto be broken by means of a switch member c which is pivotallysupportedat c upon one of thecollecting rings, the said switch mem- 7her being arranged to be moved in one direction by centrifugal force,and in the opposite direction by a yielding mechanical force as that ofa spring 0 The switch member 0 is electrically connected with thecollecting ring a, the pivot member 0 affording means for electricallyconnecting these parts, asbest shown in Fig. 1. The rings a and b areseparated from each other by a sheet of insulating material-d, so thatwhen the switch is open, there is no electrical connec:v

tion between the brushes 5 and 6. When, however, the switch is closed,the current can pass through the .brush 5 and the ring a to the switchmember 0 which,

as best shown in Fig. 2, is in electrical contact with a contact block aelectrically connected through fastening screws 6 with the collectorring I). When, there fore, the rotor is at rest, the switch Will beclosed, and when the current is turned on, the coils A and the coils Bwill both be in circuit, thus producing thephase dis placement necessaryfor starting the rotor. As soon, however, as the rotor has reached thespeed for which the switch is'adjusted, say, for example, one thousandrevolutions per minute, the centrifugal force acting on the switchmember 0 will overcome the stress of the spring and cause the saidswitch member 0 to move to the position shown in dotted lines, Fig. 2,such movement being limited by means of a stop 0. This breaks thecircuit through the coils B cutting out the said coils and leaving theworking winding A alone in circuit. i In order to prevent the closing ofthe switch in response to a slight reduction in speed, the arrangementis such that the effective force of the spring 0 is less when the switchis open than it is when the switch is closed, this being accomplished,as herein shown, by

connecting the spring with the switch member 0 in taining device 0 towhich the other end of the spring .is connected. This line, as clearlyindicated in the dotted line position of the switch, is moved nearer tothe axis of the pivotal support 0 when the switch is open, therebyshortening the lever-arm upon which the spring acts and reducing theefficiency of the spring as a restoring device for the switch arm. Theparts may be so adjusted, therefore, that, although the switch will notopen until the rotor has reached the velocity of, say, one thousandrevolutions per minute, the said switch will remain open until the speedhas been materially reduced, say, for example, down to five hundred orsix hundred revolutions per minute. The starting coils B, therefore,will not be cut out until the motor has reached its normal maximumspeed, but

the speed may afterwards be reduced through varia tions inlload, or forother causes, without causing the starting coils to be included in thecircuit. In order to insure a'good sliding contact between the switchmember 0 and the contact member e, the said switch member is hereinshown as provided with an arm 0 which is pivotally connected at c withthe member 0, while the contact member e has an extended contactportion-e having a curved guiding surface e, so that contact is insuredduring the preliminary movement of the member c in response to thecentrifugal force.

The supplemental arm c normally stands in such a position that thecentrifugal force developed by the rotation of the switch member willtend to throw it into contact with the surface 6 andmaintainit in suchcontact during the first part of the outward movement of the member 0. 1

In order to keep the member 0 in approximately the same position at alltimes, and at the same time to admit of the slight movement thereof, due.to centrifugal force, the said member is shown provided with a recess 0the walls of which stand at opposite sides of a lug or projection e onthe switch member 0, and thereby serve as stops to limit the pivotalmovement of the member 0?. I

In the construction shown, the operating parts of the switch areinclosed between the main body of the rotor and the collecting rings,and the whole being within the stator member, the working partsthus-being entirely inclosed. The collecting rings a and b are shown asmounted on a sleeve f which has a flange portionf on its outer surface,the sleeve being fastened, as by a set screw P, to the shaft 0 of therotor C. The collector ring b rests against a sheet of insulatingmaterial 9 interposed between the flange f 2 and the outer surface ofsaid collector ring, the insulation d being between the collecting ringa and the collecting ring b. The rings a and b and the sheets ofinsulation d and g are clamped together by means of screws h whichextendthrough from the inner surface to the flange f. The parts indicated bythe reference letters '5 and k, Fig. 2, are merely lugs cast onthemember a for the purpose of affording weight to counterbalance. themovable switch member and the parts cooperating therewith.

While the specific construction herein shown and described for thepurpose of illustrating the invention is practical and efficient, itisobvious that modifications may be made in the construction withoutdeparting from the invention.

Claims.

1. In a single phase induction motor, starting coils; collecting ringsinsulated from each other; brushes or collectors connecting said ringsrespectively with the terminals of said starting coils; a fixed switchmember electrically connected with one of said collecting rings; apivoted switch member electrically connected with the other of saidcollecting rings and adapted to be operated by centrifugal force; andmeans for exerting a mechanical force in opposition to said centrifugalforce and shifting the line through which said mechanical force actswith relation to the pivotal axis of the switch member.

2. In an electric switch, a rotary support provided with a fixed contactand with a pivotally supportedswitch member adapted to be moved awayfrom said fixed contact by centrifugal force; means for resisting saidcentrifugal force; and a contact member pivotally conneci'ed with saidswitch member and so positioned as to be retained by centrifugal forcein contact witlrsaid fixed contact while the switch remains closed.

In a single phase induction motor, starting coils; collecting ringsinsulated from each other; brushes or collectors connecting said ringsrespectively with the terminals'of said starting coils; a fixed switchmember electrically connected with one of said collecting rings; acentrifngally operated switch member electrically connected with theother of said collecting rings; a spring to act against the centrifugalforce in the operation of said movable switch member; and means forvarying the line of pull of said spring with relation to ,the axis ofsaid movable contact member, substantially as described.

4. In an electric switch, a rotary support; a fixed contact thereon; acooperating movable contact carried by said support and insulated fromsaid fixed contact and normally engaging but adapted to be moved out ofengagement with said fixed contact. by centrifugal force; and means forexerting a mechanical force in opposition to said centrifugal force, andshifting the line through which such mechanical force acts with relationto the pivotal axis of the switch member. I

In testimony whereof, I have signed my name to this specification in thepresence of two subscribing witnesses.

DONALD M. BLISS.

